Definitions range from general to specific aspects and from quantitative to qualitative dimensions. Initially, researchers were optimistic about the possibility to define and measure job performance. However, soon enough they started to realise that determining the dimensions of a job and its performance requirements was not a straightforward process. Nowadays it is generally agreed that job performance consists of complicated series of interacting variables pertaining to aspects of the job, the employee and the environment (Milkovich et al 1991 pp. 48-49).